Dip coating of cylinders with Newtonian fluids
Dip coating of cylinders with Newtonian fluids
复制标题
用牛顿流体对气缸进行浸涂
DOI：
10.1016/j.jcis.2021.08.181
复制
发表时间：
2022
影响因子：
9.9
通讯作者：
Kornev, Konstantin G
中科院分区：
文献类型：
--
作者：
Zhang, Zhao;Salamatin, Arthur;Peng, Fei;Kornev, Konstantin G
朗道-列维-德亚金（Landau-Levich-Derjaguin，LLD）理论被广泛应用于预测浸涂过程中的膜厚。然而，该理论仅适用于平板和薄纤维。50年前，白色和Tallmadge试图推广LLD理论，厚棒使用静态弯月面的数值解和LLD理论，以强制匹配他们的数值解与LLD渐近。White-Talmadge解决方案因不严格而受到批评，但在工程应用中广泛使用，主要是由于缺乏替代解决方案。一组新的实验显着扩大了怀特-塔尔梅奇条件的范围，表明他们的理论不能解释实验结果。然后，我们假设LLD理论的结果可以通过恢复方程中的非线性弯月面曲率来改善。通过这种修改，得到的方程应该能够描述任何圆柱形棒和膜剖面上观察到的非零rod velocity.ExperimentTo测试的假设，我们区分毛细管力从粘性力通过运行实验与不同的棒，并在不同的退出速度和视频跟踪的pecracci配置文件和测量沉积膜的重量。膜厚的值，然后拟合的数学模型的基础上修改的LLD方程。我们还拟合了弯月面profiles.FindingsThe结果表明，推导出的方程允许一个重现的LLD理论的结果，并远远超出那些包括不同半径的棒。用修正的LLD理论解释了一组新的实验数据和White-Tallmadge实验数据。一组简单的公式近似的数值结果已被推导出来。这些公式可用于工程应用中涂层厚度的预测。
HypothesisThe Landau-Levich-Derjaguin (LLD) theory is widely applied to predict the film thickness in the dip-coating process. However, the theory was designed only for flat plates and thin fibers. Fifty years ago, White and Tallmadge attempted to generalize the LLD theory to thick rods using a numerical solution for a static meniscus and the LLD theory to forcedly match their numeric solution with the LLD asymptotics. The White-Talmadge solution has been criticized for not being rigorous yet widely used in engineering applications mostly owing to the lack of alternative solutions. A new set of experiments significantly expanding the range of White-Tallmadge conditions showed that their theory cannot explain the experimental results. We then hypothesized that the results of LLD theory can be improved by restoring the non-linear meniscus curvature in the equation. With this modification, the obtained equation should be able to describe static menisci on any cylindrical rods and the film profiles observed at non-zero rod velocity.ExperimentTo test the hypothesis, we distinguished capillary forces from viscous forces by running experiments with different rods and at different withdrawal velocities and video tracking the menisci profiles and measuring the weight of deposited films. The values of film thickness were then fitted with a mathematical model based on the modified LLD equation. We also fitted the meniscus profiles.FindingsThe results show that the derived equation allows one to reproduce the results of the LLD theory and go far beyond those to include rods of different radii. A new set of experimental data together with the White-Tallmadge experimental data are explained with the modified LLD theory. A set of simple formulas approximating numeric results have been derived. These formulas can be used in engineering applications for the prediction of the coating thickness.